1. Field of the Invention
The present invention relates in general to an ink jet print head, and more particularly to such an ink jet print head which has a novel structure that assures improved and stable ink-jetting characteristics or capability, and which is available at a reduced cost.
2. Discussion of the Prior Art
In the recent market of printers used as an output device of a computer or others, there is a rapidly increasing demand for an ink jet printer which operates quietly at a relatively low cost. The ink jet printer includes an ink jet print head which is generally adapted to raise the pressure in an ink chamber filled with a mass of ink, to thereby jet or discharge fine ink particles from nozzles so as to effect printing.
There is known one type of the ink jet print head which has a piezoelectric/electrostrictive element disposed on a wall of the ink chamber, as means for raising the pressure in the ink chamber as described above. In this type of print head, a volume of the ink chamber is changed upon energization and displacement of the piezoelectric/electrostrictive element. The ink jet print head of this type is advantageous in reduced consumption of electric power, as compared with another type of ink jet print head which is adapted to heat the ink by a heater disposed in the ink chamber, to generate minute bubbles used for jetting the fine ink particles.
Referring to FIGS. 5 and 6 showing an example of the above type of the ink jet print head, a metallic nozzle plate 4 having a plurality of nozzles 2, a metallic orifice plate 8 having a plurality of orifices 6, and a channel plate 10 are superposed on each other such that the channel plate 10 is interposed between the plates 4, 8, and these plates 4, 8, 10 are bonded together into an ink nozzle member 16. In this ink nozzle member 16, there are formed a plurality of ink discharge channels 12 for leading or guiding an ink material to the respective nozzles 2, and at least one ink supply channel 14 for leading or supplying the ink material to the orifices 6. The ink jet print head further includes an ink pump member 24 which consists of two plates 18, 20 made of metal or synthetic resin and formed in lamination on the ink nozzle member 16. The ink pump member 24 has a plurality of voids 22 which correspond to the nozzles 2 and orifices 6. With this ink pump member 24 superposed on and bonded to the ink nozzle member 16, each of the voids 22 provides an ink chamber 26 formed behind the corresponding nozzle and orifice 2, 6. The ink jet print head also includes a plurality of piezoelectric/electrostrictive elements 28 each of which is secured to a wall of the corresponding ink chamber 26 remote from the ink nozzle member 16.
In producing the above type of ink jet print head, however, small pieces of the piezoelectric/electrostrictive elements 28 must be bonded to the walls of the respective ink chambers 26, which makes it extremely difficult to render the resulting print head sufficiently small-sized. Further, the bonding of the piezoelectric/electrostrictive elements 28 inevitably pushes up the cost of manufacture of the print head, and makes it difficult for the elements 28 to maintain sufficiently high reliability.
In the production of the above-described ink jet print head, another problem arises when the ink nozzle member 16 and the ink pump member 24 are bonded together. Namely, the spacing between the adjacent voids 22, 22 formed in the print head, that is, the thickness "t" of a partition wall 30 which separates the adjacent voids from each other, is considerably small, more precisely, about 1 mm or smaller. Such a small spacing between the voids 22 makes it extremely difficult to bond the ink nozzle member 16 and the ink pump member 24 to each other.
More specifically, an adhesive used for bonding the ink nozzle member 16 and the ink pump member 24 is likely to overflow onto the opposite surfaces of the partition wall 30. Therefore, the ink chambers 26 and/or ink flow channels including the ink supply and discharge channels 12, 14 and orifices 6 may be deformed, whereby the ink-jetting characteristics of the print head may deteriorate, resulting in reduced quality and yield of the products (print heads).
If the amount of the adhesive applied is reduced to avoid its overflow as described above, it is likely that the ink nozzle member 16 and ink pump member 24 are insufficiently or poorly bonded together at some portions of the interface of the members 16, 24. This may result in incomplete sealing between the adjacent ink chambers 26, 26, causing leakage of the pressures of the ink chambers 26, 26 and consequent crosstalk, for example. The partial or insufficient bonding may also leave gaps between the bonding surfaces of the members 16, 24, resulting in pressure loss upon pressurizing of the ink chambers 26 due to the air remaining in the gaps. Consequently, the ink-jetting characteristics of the print head may be lowered.